Parasitic captures

Phagotrophy is a fourth means by which the parasite captures Hb. Many phagosomes appear at the trophozoite and schizont stages. Unlike typical phagosome found in other eukaryotes, their formation is not actin-dependent and very similar in mechanism to the big gulp [21]. 

The moderator temperature reactivity coefficient is also important for safety. In fact, when the moderator temperature increases, its density decreases and, as a consequence, the moderating effectiveness also decreases. This decrease causes an increase in the loss of neutrons from the core and an increase in the parasite captures, so that the reactivity tends to decrease. 

This relation assumes an average load factor of 70% for the entire system of nuclear generating stations. The a is the ratio of parasitic capture to fission for the initial and bred fuel, appropriately averaged CR is the average conversion ratio and MJM2S is, again, the ratio of total uranium to recoverable In this case, however, allowance must be made for U discarded at the end of the fuel cycle, if the final enrichment is such that the is not economically recoverable. 

A completely different scenario involves the utilization of the neutrons otherwise lost by parasitic capture in the control materials of the "client" fission reactors. For example, using °Li and/or He (instead of etc.) as control materials in Light Water Reactors, one could arrive at y s (y = No. of tritons produced per average fusion neutron) close to 0.75.[43] This would support a SCD-T mode of operation having about 5 fold the power density of the corresponding SCO plasma. 

Non-fission capture by the graphite, structural materials, coolant, fission products, etc. (parasitic capture). x... 

Answer By withdrawing the neutron-absorbing control rods, the parasitic capture of neutrons is reduced so lliat k ff becomes greater than one and the rising chain reaction causes the neutron density to increase until the desired power level is attained. The control rods are then partially inserted to absorb enou neutrons to make keff equal to unity the chain reaction now becomes steady and the power level remains constant. 

The neutron absorption cross-sections of any liquid salt for reactor applications must be low to avoid excessive parasitic capture of neutrons. For thermal and intermediate neutron spectrum reactors, this probably eliminates chloride salts with their higher nuclear cross sections, even if the high cross section Cl is removed. Only fluoride salts are candidates. A wide variety of atoms have low cross sections however, the realistic candidates are also restricted by the requirements of thermodynamic stability to ensure viable materials of construction for the container. Table XXVI-5 shows the primary salt options and their cross sections. If either lithium or boron is used as a salt component, isotopically separated lithium and boron are required to have a salt with a low absorption cross section. 

Hafnium Rods No off-gassing and strong parasitic capture. 

Ag-In-Cd Rods Large industry experience, expensive, may not be black enough for pluionium fuel, exhibits parasitic capture over broad energy range. 

Neutron balance and miscellaneous details. Details of the neutron economy of a reactor fueled with plutonium are given in Table 14-7. Parasitic captures in Pu are relatively high y is 1.84, compared with a, v oi 2.9. The neutron spectrum is relatively soft almost 60% of all fissions are caused by thermal neutrons and, as a result, absorptions in lithium are high. 

The limitations of motallurgical knowledge at present lead to the conclusion that tantalum will be one of the be.st container materials for those plutonium alloys. The high-temperature strength properties and the heat-transfer properties of tantalum are excellent moreover, it is weldable. The parasitic capture cross section of tantalum would be intolerable in an epithermal or thermal power breeder reactor and, although relatively large in a fast spectrum, its effect on neutron economy in a fast reactor can be made small, if not minor, by careful design. 

AntihBiminticS Flubendazole was launched as an antihelmintic. It seems to have a mode of action close to that of benzimidazole derivatives used as antihelmintics mebendazole, albendazole), which are reported to block the capture of glucose by the parasite (Figure 8.23). 

The possibility that parasites can synthesise host or host-like antigens raises the question of whether or not parasites can make use of mRNA to synthesise host protein (799) or whether putative molecular mimicry may actually represent cases of host capture by parasites via natural transfection (perhaps by retroviruses ) - a hypothesis reviewed in detail by Howell (338). It has been pointed out earlier (Chapter 8) that there is evidence to suggest that this may have occurred in the sparganum of Spirometra mansonoides, which is capable of synthesising a growth factor with properties resembling those of a mammalian growth hormone (Tables 8.8 (p. 218) and 8.9 (p. 219)). 

Hb digestion requires specialized structures which are organized by the parasite as soon as it enters the ring stage, but are modulated in importance throughout the cell cycle. Several mechanisms have been proposed for the capture of Hb by the parasite [20-24]. 

Figure 11.6. Parasitic power loss for power plants with C02 capture (percent of net power plant power) with state-of-the-art scrubbing technologies.

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